1. Field of the Invention
The present invention relates to, in particular, an art of accessing a storage apparatus such as a hard disk apparatus or such from a client apparatus such as a personal computer (simply referred to as a ‘PC’ hereinafter) or a work station (simply referred to as a ‘WS’, hereinafter).
2. Description of the Related Art
A so-called storage system has been applied for a wide variety of fields, in which, for example, a storage apparatus such as a hard disk apparatus is physically connected to a client apparatus such as a PC, a WS or such, via an interface such as an SCSI (small computer system interface), an FC (fiber channel) or such.
FIG. 25 shows one example of such a storage system in the related art.
The storage system shown in FIG. 25 includes a client apparatus 100 such as a PC, a bus 300 connected to an SCSI card 103, and an input/output apparatus 200 having a disk apparatus 203 or such. The client apparatus 100 and the input/output apparatus 200 are connected via the bus 300. The client apparatus 100 includes a CPU 101, a main memory 102, the SCSI card 103 and an internal bus 104. The CPU 101 and the main memory 102 are connected via the internal bus 104 in such a manner that they can communicate with one another therewith. The internal bus 104 is connected to the SCSI bus 103. Further, the main memory 102 has a file system 105 and an SCSI driver 106 incorporated therein for providing functions of an OS (operating system).
The input/output apparatus 200 includes a disk controller 201, a buffer 202 and the disk apparatus 203. The disk apparatus 203 is connected with the disk controller 201 via the buffer 202, and the disk controller 201 is connected with the bus 300.
In the storage system, when data is written in the input/output apparatus 200 by the client apparatus 100, for example, the following processing is carried out.
That is, the OS (file system 105) of the client apparatus 100 makes writing request to the SCSI driver 106 for the disk apparatus 203 (A1). The SCSI driver 106 repeats negotiation for determining a data transfer rate with the disk controller 201 several times, and then, set a path on the bus 300 (A2). After the path is thus set, the client apparatus 100 requests the disk controller 201 for data writing so as to first start data transfer (A3). In this case, when a time is required for data writing in the input/output apparatus 200, the SCSI driver 106 once cancels the path with the disk controller 201.
The disk controller 201 of the input/output apparatus 200 stores data received from the client apparatus 100 in the buffer 202 temporarily (A4), and then, writes the received data in the disk apparatus 203 (A5). When the data writing in the input/output apparatus 200 is finished, the disk controller 201 reports this writing finish to the SCSI driver 106 with an interrupt (A8). The SCSI 106 reports the transfer completion to the file system 105 (A9).
In the storage system in the related art, when the client 100 makes data transfer to the input/output apparatus 200, the disk controller 201 should be first started up according to a protocol prescribed in the SCSI, FC or such in the input/output apparatus 200. Further, until data transfer is actually commenced by the client apparatus 100 to the input/output apparatus 200, a plurality of times of negotiation should be made for the purpose of determining the transfer rate as mentioned above. Accordingly, a latency (waiting time) required for actually starting the data transfer may be long, and also, a procedure carried out after the commencement of the data transfer may be complicated.
Further, the data transfer rate with the use of the interface such as the SCSI, FC or such is at most 160 Mbytes/sec. Therefore, development should be proceeded for a higher speed input/output technology for a next generation. Otherwise, a high speed transmission band such as 2.5 Gbps, 10 Gbps, 30 Gbps or such of an InfiniBand (a trademark of InfiniBand (SM) Trade Association, abbreviated as an ‘IB’, hereinafter) or such for example, may not be effectively utilized.
For example, Japanese Laid-open Patent Application No. 2003-6137 (in particular, paragraphs 0010 through 0020, FIG. 1 or such) discloses a storage system for solving the problem. This storage system includes a client apparatus, an input/output apparatus, a connecting part connecting therebetween, a virtual address managing part managing virtual address information and physical address information of the input/output apparatus in such a manner that relationship therebetween is provided, and a control part controlling data transfer between the client apparatus and the input/output apparatus based on the virtual address information managed by the managing part. Thereby, the complicated negotiation required for the commencement of data transfer from the client apparatus to the input/output apparatus can be omitted.
On the other hand, a development of a system enabling dividing processing for dividing a given processing load among a plurality of servers has been proceeded actively for solving a problem that a large amount of data should be processed at a high speed. However, for achieving this object, a high speed file access technology is required in which a plurality of servers can access a common data resource, and also, an arbitrary server can access an arbitrary data resource. For this purpose, a development of a file sharing protocol called a direct access file system (abbreviated as ‘DAFS’ hereinafter) has been promoted which conforms to the transmission band of the above-mentioned IB for example. The DAFS is achieved with the use of remote direct memory access (abbreviated as an ‘RDMA’ hereinafter) technology or such in which a memory of a different client apparatus may be directly accessed (see a Web site, http://www/dafs01.html (“special plan, technology description for ‘DAFS’”, Mar. 17, 2003).